U.S. patent application number 12/000961 was filed with the patent office on 2009-06-25 for resilient ppp/ml-ppp services over multi-chassis aps protected routers.
This patent application is currently assigned to ALCATEL LUCENT. Invention is credited to Kajal Saha.
Application Number | 20090161535 12/000961 |
Document ID | / |
Family ID | 40717093 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090161535 |
Kind Code |
A1 |
Saha; Kajal |
June 25, 2009 |
Resilient PPP/ML-PPP services over multi-chassis APS protected
routers
Abstract
A system and method for resilient communication services under
multi-chassis APS protected routers, including one or more of the
following: an add-drop multiplexer; a working chassis; a plurality
of working lines of communication between the add-drop multiplexer
and the working chassis; a protection chassis; a plurality of
protection lines of communication between the add-drop multiplexer
and the protection chassis; and a multi-chassis APS control link
between the working chassis and the protection chassis, wherein a
plurality of active entities in the working chassis having state
information send their state information to parallel inactive
entities in the protection chassis by way of the multi-chassis APS,
ones of said active entities send changed state information to
parallel ones of said inactive entities through said multi-chassis
APS control link upon a state change in said ones of said active
entities, and ones of said inactive entities that were down request
current state information from said active entities through said
multi-chassis APS control link when said ones of said inactive
entities that were down come back up after being down.
Inventors: |
Saha; Kajal; (Ottawa,
CA) |
Correspondence
Address: |
KRAMER & AMADO, P.C.
1725 DUKE STREET, SUITE 240
ALEXANDRIA
VA
22314
US
|
Assignee: |
ALCATEL LUCENT
Paris
FR
|
Family ID: |
40717093 |
Appl. No.: |
12/000961 |
Filed: |
December 19, 2007 |
Current U.S.
Class: |
370/221 |
Current CPC
Class: |
H04L 49/557 20130101;
H04L 45/00 20130101; H04L 1/1642 20130101; H04L 45/24 20130101;
H04L 45/586 20130101; H04L 45/22 20130101; H04L 45/28 20130101 |
Class at
Publication: |
370/221 |
International
Class: |
G06F 11/00 20060101
G06F011/00 |
Claims
1. A system for resilient communication services under
multi-chassis APS protected routers, comprising: an add-drop
multiplexer; a working chassis; a plurality of working lines of
communication between the add-drop multiplexer and the working
chassis; a protection chassis; a plurality of protection lines of
communication between the add-drop multiplexer and the protection
chassis; and a multi-chassis APS control link between the working
chassis and the protection chassis, wherein a plurality of active
entities in the working chassis having state information send their
state information to parallel inactive entities in the protection
chassis by way of the multi-chassis APS, ones of said active
entities send changed state information to parallel ones of said
inactive entities through said multi-chassis APS control link upon
a state change in said ones of said active entities, and ones of
said inactive entities that were down request current state
information from said active entities through said multi-chassis
APS control link when said ones of said inactive entities that were
down come back up after being down.
2. The system for resilient communication services over
multi-chassis APS protective routers, according to claim 1, wherein
said plurality of working lines and said plurality of protection
lines operate under a point-to-point protocol.
3. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said plurality of working lines and said plurality of protection
lines operate under a multilink point-to-point protocol.
4. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said plurality of active entities and said parallel inactive
entities are point-to-point protocol entities, a number of said
plurality of active entities is at least 500, said working chassis
and said protection chassis have ports, and a data outage during an
APS switchover lasts less than one and a half seconds per port.
5. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 4, wherein
said data outage during said APS switchover lasts less than 1.2
seconds per port.
6. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said working chassis and said protection chassis are SONET/SDH
physical ports.
7. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said working chassis and said protection chassis are configured in
SONET/SDH line terminating equipment.
8. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
the said working chassis and said protection chassis include
parallel point-to-point protocol communications end points.
9. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said multi-chassis APS control link is an Internet protocol
connection.
10. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said plurality of active entities and said parallel inactive
entities are point-to-point protocol entities and a data outage
during an APS switchover lasts less than 2.5 milliseconds per
point-to-point protocol entity.
11. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said multi-chassis APS control link sends communications via a
proprietary protocol.
12. The system for resilient communication services over
multi-chassis APS protected routers, according to claim 1, wherein
said working chassis and said protection chassis each include an
eight port router and each eight port router achieves a fully
operational state following an APS switchover including all eight
ports in less than ten seconds.
13. A method for a resilient communication services over
multi-chassis APS protected routers, comprising: all active
entities in a working chassis having state information sending that
state information to parallel inactive entities in a protection
chassis through a multi-chassis APS control link that travels
between the working chassis and the protection chassis; ones of
said active entities sending changed state information from said
working chassis to said protection chassis through said
multi-chassis APS control link upon a state change of said ones of
said active entities; and ones of said inactive entities requesting
current state information from said all active entities through
said multi-chassis APS control link when said ones of said inactive
entities come back up after being down.
14. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said state information is state information of communications under
a point-to-point protocol.
15. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said state information is state information of communications under
a multilink point-to-point protocol.
16. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said active entities and said inactive entities are point-to-point
protocol entities, said working chassis and said protection chassis
have ports, and a data outage during an APS switchover lasts less
than one and a half seconds per port.
17. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 16, wherein
said data outage during said APS switchover lasts less than 1.2
seconds per port.
18. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said working chassis and said protection chassis are SONET/SDH
physical ports.
19. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said working chassis and said protection chassis are configured in
SONET/SDH line terminating equipment.
20. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
the said working chassis and said protection chassis include
parallel point-to-point protocol communications end points.
21. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said multi-chassis APS control link is an Internet protocol
connection.
22. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said active entities and said inactive entities are point-to-point
protocol entities and a data outage during an APS switchover lasts
less than 2.5 milliseconds per point-to-point protocol entity.
23. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said multi-chassis APS control link sends communications via a
proprietary protocol.
24. The method for a resilient communication services over
multi-chassis APS protected routers, according to claim 13, wherein
said working chassis and said protection chassis each include an
eight port router and each eight port router achieves a fully
operational state following an APS switchover in less than ten
seconds.
25. A communication method for resilient communication services
over multi-chassis APS protected routers, comprising: sending one
or more packets with one or more sequence numbers from a plurality
of active entities in a working chassis to a plurality of parallel
inactive entities in a protection chassis by way of a multi-chassis
APS control link passing between said working chassis and said
protection chassis; receiving said one or more packets with said
one or more sequence numbers at the plurality of parallel inactive
entities in said protection chassis; sending one or more
acknowledgements with said one or more sequence numbers from said
plurality of parallel inactive entities in said protection chassis
to said active entities in said working chassis through said
multi-chassis APS control link; and receiving said one or more
acknowledgements with said one or more sequence numbers at said
active entities in said working chassis
26. A method for a resilient communications services over
multi-chassis APS protective routers, comprising: all active
entities in a working chassis having state information sending that
state information to parallel inactive entities in a protection
chassis through a multi-chassis APS control link that travels
between the working chassis and the protection chassis; determining
that a control link is down; determining that the control link that
was down has come back up; and all active entities in the working
chassis again sending the state information to the parallel
inactive entities in the protection chassis through the
multi-chassis APS control link.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to point-to-point protocol
(PPP) communications using automatic protection switching
(APS).
[0003] 2. Description of Related Art
[0004] In networking, the PPP is a data link protocol used to
establish a direct connection between two nodes over serial cable,
phone line, trunk line, cellular telephone, specialized radio
links, or fiber optic links. Most Internet service providers use
PPP for customers' dial-up access to the Internet. Two common
encapsulated forms of PPP, Point-to-Point Protocol over Ethernet
(PPPoE) or Point-to-Point Protocol over ATM (PPPoA), are used in a
similar role with Digital Subscriber Line (DSL) Internet
service.
[0005] Asynchronous Transfer Mode (ATM) is a cell relay, packet
switching network and data link layer protocol which encodes data
traffic into small fixed-sized cells. ATM provides data link layer
services that run over Layer 1 links. ATM differs from other
technologies based on packet-switched networks such as the Internet
Protocol or Ethernet which use variable sized packets known as
frames when referencing layer 2. ATM is a connection-oriented
technology, in which a logical connection is established between
the two endpoints before the actual data exchange begins.
[0006] PPP is often used to act as a data link layer protocol for
connection over synchronous and asynchronous circuits. For such
uses, PPP has largely superseded the older, non-standard Serial
Line Internet Protocol (SLIP), and standards mandated by telephone
companies such as Link Access Protocol, Balanced (LAPB) in the X.25
protocol suite. PPP was designed to work with numerous network
layer protocols, including Internet Protocol (IP).
[0007] One approach to failure detection in routers used for PPP
communications is APS. In distributed routing systems with APS
protection on routers, multilink PPP (MLPPP or ML-PPP) is an
extension to the PPP. MLPPP is a bandwidth-on-demand protocol that
can connect multiple links between two systems as needed to provide
bandwidth on demand. The technique is often called bonding or link
aggregation.
[0008] For example, the two 64-Kbit/sec B channels of ISDN can be
combined to form a single 128-Kbit/sec data channel. Another
example would be to bind one or more dial-up asynchronous channels
with a leased synchronous line to provide more bandwidth at peak
hours of the day.
[0009] Many PPP and ML-PPP communications systems using APS routers
experience a temporary data loss during an APS switch. This data
loss is undesirable. Thus, there is a need for a mechanism and
method that minimizes data loss in PPP/ML-PPP communications
systems using APS routers during an APS switch.
[0010] The foregoing objects and advantages of the invention are
illustrative of those that can be achieved by the various exemplary
embodiments and are not intended to be exhaustive or limiting of
the possible advantages which can be realized. Thus, these and
other objects and advantages of the various exemplary embodiments
will be apparent from the description herein or can be learned from
practicing the various exemplary embodiments, both as embodied
herein or as modified in view of any variation which may be
apparent to those skilled in the art. Accordingly, the present
invention resides in the novel methods, arrangements, combinations
and improvements herein shown and described in various exemplary
embodiments.
SUMMARY OF THE INVENTION
[0011] Multi-chassis MLPPP is a specific category within the
broader category of MLPPP. In light of the present need for
resilient PPP/ML-PPP services over multi-chassis APS protected
routers, a brief summary of various exemplary embodiments is
presented. Some simplifications and omission may be made in the
following summary, which is intended to highlight and introduce
some aspects of the various exemplary embodiments, but not to limit
its scope. Detailed descriptions of a preferred exemplary
embodiment adequate to allow those of ordinary skill in the art to
make and use the invention concepts will follow in later
sections.
[0012] A multi-chassis APS switchover typically causes the APS
protected port of a standby router to become active. In various
exemplary embodiments, after a multi-chassis APS switchover, the
PPP/MLPPP links or bundles over the APS port in a newly active
router typically need to renegotiate all the PPP/MLPPP protocols
with their peers. This often results in a significant period during
an APS switchover when the transfer of data is interrupted. This
interruption in the transfer of data is referred herein as a data
outage.
[0013] In various exemplary embodiments, hundreds of PPP/MLPPP
links or bundles run over an APS protected port. In such
embodiments, the data outage that occurs during a multi-chassis APS
switchover is often of such length that it causes one or more of
the end applications relying on the PPP/MLPPP links or bundles to
disconnect or terminate. Also, during an APS chassis or router
reboot thousands of PPP/MLPPP links or bundles will be switched to
the new router or chassis. For example, in applications pertaining
to telephone calls, an APS switchover, including during router
reboot, could result in the loss of a significant quantity of
connected telephone calls. Various exemplary embodiments overcome
such an excessive data outage over multi-chassis APS protected
PPP/MLPPP links or bundles during an APS switchover.
[0014] In various exemplary embodiments, the PPP/MLPPP states of
links or bundles from an active router are synchronized to a
standby router. Accordingly, various exemplary embodiments
eliminate a need to renegotiate PPP/MLPPP protocols upon a
multi-chassis APS switchover. This results in a corresponding
reduction of the length or significance of a data outage during a
multi-chassis APS switchover. In various exemplary embodiments, as
will be described in greater detail below, the extent of the
reduction in the data outage during a multi-chassis APS switchover
is significant.
[0015] Various exemplary embodiments are a system for resilient
communication services under multi-chassis APS protected routers,
including: an add-drop multiplexer; a working chassis; a plurality
of working lines of communication between the add-drop multiplexer
and the working chassis; a protection chassis; a plurality of
protection lines of communication between the add-drop multiplexer
and the protection chassis; and a multi-chassis APS control link
between the working chassis and the protection chassis, wherein a
plurality of active entities in the working chassis having state
information send their state information to parallel inactive
entities in the protection chassis by way of the multi-chassis APS,
ones of said active entities send changed state information to
parallel ones of said inactive entities through said multi-chassis
APS control link upon a state change in said ones of said active
entities, and ones of said inactive entities that were down request
current state information from said active entities through said
multi-chassis APS control link when said ones of said inactive
entities that were down come back up after being down. The
respective roles of the working and protection chassis in various
exemplary embodiments are discussed further herein.
[0016] Various exemplary embodiments are a method for a resilient
communication services over multi-chassis APS protected routers,
including: all active entities in a working chassis having state
information sending that state information to parallel inactive
entities in a protection chassis through a multi-chassis APS
control link that travels between the working chassis and the
protection chassis; ones of said active entities sending changed
state information from said working chassis to said protection
chassis through said multi-chassis APS control link upon a state
change of said ones of said active entities; and ones of said
inactive entities requesting current state information from said
all active entities through said multi-chassis APS control link
when said ones of said inactive entities come back up after being
down.
[0017] Various exemplary embodiments are a communication method for
resilient communication services over multi-chassis APS protected
routers, including: sending one or more packets with one or more
sequence numbers from a plurality of active entities in a working
chassis to a plurality of parallel inactive entities in a
protection chassis by way of a multi-chassis APS control link
passing between said working chassis and said protection chassis;
receiving said one or more packets with said one or more sequence
numbers at the plurality of parallel inactive entities in said
protection chassis; sending one or more acknowledgements with said
one or more sequence numbers from said plurality of parallel
inactive entities in said protection chassis to said active
entities in said working chassis through said multi-chassis APS
control link; and receiving said one or more acknowledgements with
said one or more sequence numbers at said active entities in said
working chassis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to better understand various exemplary embodiments,
reference is made to the accompanying drawings, wherein:
[0019] FIG. 1 is a schematic diagram of a first exemplary
embodiment of a system for resilient PPP/ML-PPP services over
multi-chassis APS protected routers;
[0020] FIG. 2 is a schematic diagram of a second exemplary
embodiment of a system for resilient PPP/ML-PPP services over
multi-chassis APS protected routers;
[0021] FIG. 3 is a flow chart of an exemplary embodiment of a
method for resilient PPP/ML-PPP services over multi-chassis APS
protected routers; and
[0022] FIG. 4 is a flow chart of an exemplary embodiment of a
method for sending state information in resilient PPP/ML-PPP
services over multi-chassis APS protected routers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0023] Referring now to the drawings, in which like numerals refer
to like components or steps, there are disclosed broad aspects of
various exemplary embodiments.
[0024] FIG. 1 is a schematic diagram of a first exemplary
embodiment of a system 100 for resilient PPP/ML-PPP services over
multi-chassis APS protected routers. System 100 is an example
involving one APS group. In system 100, a single working line (WL)
120 connects Add-Drop multiplexer (ADM) 115 with the working
chassis 135. Likewise, a single protection line (PL) 125 connects
ADM 115 with protection chassis 145. In various exemplary
embodiments, the working chassis 135 and the protection chassis 145
are selected from the 7710 and 7750 models.
[0025] Accordingly, the APS group 130 includes a working circuit
and a protection circuit. In various exemplary embodiments, the
working circuit is a synchronous optical network
(SONET)/synchronous digital hierarchy (SDH) physical port.
[0026] The terms working and active are used interchangeably herein
under normal operating conditions. Likewise, the terms protection
and inactive are used interchangeably herein. Further, it should be
apparent that the roles respectively described herein for the two
are reversed upon a switchover in a non-revertive mode. It should
also be apparent that, in a revertive mode, the roles respectively
described herein for the two are reversed back again as soon as a
working circuit becomes available again.
[0027] In various exemplary embodiments, the APS group 130
including the working circuit and the protection circuit is
configured in a SONET/SDH line terminating equipment (LTE)/chassis.
Accordingly, system 100 includes working chassis 135 and protection
chassis 145. This arrangement is sometimes referred to herein as a
one plus one (1+1) arrangement. In system 100, DS1 105 represents a
PPP/MLPPP terminating node or end point 1. DS1 105 is connected to
ADM 115 by way of links, for example DS1, or bundles 110.
[0028] In system 100, the multi-chassis (MC) APS 1+1 feature
enables the protection circuit and the working circuit to be
configured in two different chassis or routers. Again, this is
depicted by way of separate working chassis 135 and protection
chassis 145.
[0029] The multi-chassis/router APS signaling is accomplished in
system 100 between the working chassis 135 and the protection
chassis 145 by way of MC-APS control link 140. The MC-APS control
link 140 is a control link that usually passes directly between the
working chassis 135 and the protection chassis 145. It should be
apparent that, in various exemplary embodiments, the APS control
link 140 passes indirectly between the working chassis 135 and the
protection chassis 145. However, the MC-APS control link 140 does
not pass between the working chassis 135 and the protection chassis
145 by way of the ADM 115. Accordingly, in various exemplary
embodiments, the MC-APS control link 140 is an IP connection.
[0030] Based on the foregoing, the MC-APS feature 150 of system 100
protects against nodal or router failures in addition to the link
and circuit failures discussed above. Accordingly, in the case of a
failure or degradation of a signal in one physical link or circuit,
the other circuit is able to quickly take over.
[0031] In various exemplary embodiments, the working chassis 135
represents a PPP/MLPPP end point 2 and the protection chassis 145
also represents the same PPP/MLPPP end point 2. Further, it should
be noted that the references herein to PPP end point 1 in DS1 box
105 and PPP/MLPPP end point 2 in working chassis 135 and protection
chassis 145 should also be understood to be references, in various
exemplary embodiments, to PPP/MLPPP end points.
[0032] In various exemplary embodiments, hundreds of PPP/MLPPP
links or bundles run over a single APS group 130. Further, in
various exemplary embodiments, multiple APS groups are configured
between the working chassis 135 and the protection chassis 145. In
various exemplary embodiments, the PPP/MLPPP protocol is a link
control protocol (LCP), an Internet protocol control protocol
(IPCP), a bridge control protocol (BCP), and so on.
[0033] FIG. 2 is a schematic diagram of a second exemplary
embodiment of a system 200 for resilient PPP/ML-PPP services over
multi-chassis APS protected routers. The ADM 115, APS group 130,
working chassis 135, MC-APS control link 140, protection chassis
145, and MC-APS 150 in system 200 are essentially the same as
described above in connection with system 100. Accordingly, common
reference numbers are used between system 100 and system 200 when
referring to these components.
[0034] System 200 includes a plurality of working lines WL-1 to
WL-n. Likewise, system 200 includes a plurality of protection lines
PL-1 to PL-n. Accordingly, it should be understood that n
represents an integer variable greater than 1. The protection lines
PL-1 to PL-n travel between ADM 115 and protection chassis 145 just
as protection line 125 in system 100. Likewise, the working lines
WL-1 to WL-n travel from ADM 115 to working chassis 135 just as
working line 120 in system 100.
[0035] Each working line WL-1 to WL-n, and each protection line
PL-1 to PL-n, corresponds to a port. Accordingly, each working line
WL-1 to WL-n and each protection line PL-1 to PL-n corresponds to
approximately 512 PPP entities because there are typically around
512 PPP/MLPPP entities in one channelized port in SONET/SDH. It
should be apparent that other embodiments exist having other
numbers of PPP/MLPPP entities.
[0036] In system 200, the PPP protocol states of the links or
bundles over the active APS circuits from one chassis or router are
synchronized with those of the related links or bundles over the
inactive APS circuits in the other chassis or router. In various
exemplary embodiments, the PPP state information is sent over the
MC-APS control link 140 using a proprietary protocol. Accordingly,
various exemplary embodiments ensure the reliable delivery of state
information from one router to the other router.
[0037] In various exemplary embodiments, an inactive PPP/MLPPP
entity on one router sends a request to the active entity of the
other router to get the current PPP/MLPPP state information from
the corresponding active entity of the other router. This will be
discussed in greater detail below in connection with FIGS. 3 and
4.
[0038] After an MC-APS switchover, if the PPP/MLPPP protocol state
of the synchronized data indicates an "open" state and the newly
active physical link or bundle is operationally up, then the newly
active PPP entity runs its finite state machine (FSM) based on the
synchronized data. Accordingly, in various exemplary embodiments, a
newly active physical link or bundle following an MC-APS switchover
is able to achieve an operational state without renegotiating with
its peer. Thus, in various exemplary embodiments, services are
restored after an APS switchover much more quickly than embodiments
where a renegotiation with a peer is necessary.
[0039] It typically takes approximately fifteen seconds to
renegotiate each port in SONET/SDH where around 512 PPP/MLPPP
entities are involved in each port. Accordingly, in an application
including eight SONET/SDH ports it can take about two minutes to
renegotiate the entire application. This occurs when simultaneous
multiple port failures exist in connection with a router failure
where all eight ports of the router are involved.
[0040] In comparison, exemplary system 200 is able to achieve a
fully operational state of an eight port router in as little as
eight seconds following an APS switchover. This corresponds to less
than 2.5 milliseconds per PPP/MLPPP entity. It should be apparent
that the operational benefits of achieving an operational state
following an APS switchover in eight seconds versus two minutes is
significant. This will be discussed in greater detail below.
[0041] FIG. 3 is a flow chart of an exemplary embodiment of a
method 300 for resilient PPP/ML-PPP services over multi-chassis APS
protected routers. Method 300 starts in step 302 and continues to
step 304. Step 304 is used as a system setup procedure for systems
such as system 100 and system 200. In step 304, all active entities
send the state information to their parallel protection entities.
This communication, and all other communications described herein,
occur in system 100 and system 200 between working chassis 135 and
protection chassis 145 by way of MC-APS control link 140.
[0042] While the description of exemplary method 300 herein uses
sequential language, it should be understood that, in various
exemplary embodiments, different sequences are followed. It should
also be understood that, various steps in exemplary method 300
occur, in some embodiments, to the exclusion of other steps in
exemplary method 300. For example, in various exemplary
embodiments, steps 306 and 308 occur but steps 310, 312, 314 do not
occur. Similarly, in various exemplary embodiments, steps 310 and
312 occur, but steps 306, 308, 314 do not occur. Likewise, in
various exemplary embodiments, step 314 occurs and returns to step
304, but steps 306, 308, 310, 312 are omitted. Accordingly, the
following sequential description should be understood to describe
only one possible sequence of a multitude of possible sequences of
the various steps depicted for exemplary method 300.
[0043] Further, in various exemplary embodiments, all of the steps
in exemplary method 300 or a subset of the steps in exemplary
method 300 occur, but in a different order of sequence than the
order depicted in exemplary method 300. For example, in another
exemplary embodiment where all of the steps exists, step 314 occurs
first, steps 310 and 312 occur next, and steps 306 and 308 occur
last.
[0044] Following step 304, the method 300 proceeds to step 306. In
step 306, an analysis is made whether there has been a change in
any of the PPP/MLPPP state information on the active entity. If
there has not been a change in the PPP/MLPPP state information on
the active entity, the method 300 proceeds to step 310. If there
has been a change in the PPP/MLPPP state information on the active
entity, the method 300 proceeds to step 308.
[0045] In step 308, the active entity proactively sends the changed
state information to the inactive entity. Thus, the PPP/MLPPP state
information held on the inactive entity is maintained as current
directly in response to changes in the PPP/MLPPP state information
on the active entity. Accordingly, the communication necessary to
achieve up to date state information on the inactive entity does
not need to leave the APS group 130. Thus, such communications do
not travel to the ADM 115. Rather, such a communication travels
either directly or indirectly between the working chassis 135 and
the protection chassis 145 through the MC-APS control link 140
within the MC-APS group 130.
[0046] Following step 308, the method 300 proceeds to step 310. In
step 310, an evaluation is performed whether an inactive entity is
down. When a determination is made in step 310 that no inactive
entity is down, in other words, that all active entities are up,
the method 300 proceeds to step 314. Conversely, when a
determination is made in step 310 that an inactive entity is down,
the method 300 proceeds to step 312.
[0047] In step 312, after an inactive entity that went down comes
back up, that inactive entity requests current state information
from the active entity. Following step 312, the method 300 returns
to step 304.
[0048] At any time, when, the method 300 reaches step 314, a
determination is made whether a control link has gone down. If a
control link has gone down, a determination is made to that effect
and the method 300 proceeds to step 315. In step 315, after the
control link that was down has come back up, a determination is
made to that effect. Then, after the control link subsequently
comes back up the method 300 again returns to step 304 where the
initial setup procedure is repeated. Because it cannot be known
which, if any, of the active entities experienced a state change
while the control link was down, this corresponds essentially to a
start up procedure. Accordingly, when a control link has gone down,
all active entities send their state information to the inactive
entities.
[0049] Eventually, the method 300 will get to step 314 and a
determination will be made that no control link has gone down. When
a determination is made in step 314 that no control link has gone
down, the method 300 proceeds to step 316 where the method 300
stops.
[0050] According to the foregoing, when the associated PPP/MLPPP
protocol state information of the synchronized data indicates any
other state than open, the newly active PPP/MLPPP entity starts
renegotiating the PPP/MLPPP protocol. In this manner, traffic is
restored even in the case where the PPP/MLPPP was not up, and in
the case where the PPP/MLPPP state information was not fully
synchronized, before an MC-APS switchover.
[0051] In other words, according to method 300, it is not necessary
to renegotiate PPP/MLPPP protocol state information between the
working chassis 135 and the protection chassis 145 if all of the
synchronized data between the working chassis 135 and the
protection chassis 145 is up by way of MC-APS control link 140.
Otherwise, the PPP/MLPPP state information is renegotiated between
the working chassis 135 and the protection chassis 145 just as in
other systems that do not contain an MC-APS control link 140 for
direct synchronization of information between the working chassis
135 and the protection chassis 145.
[0052] Put differently, system 100, system 200 and method 300 do
not create any new problems. This is true because, whenever the
advantages and benefits of system 100, system 200 and method 300
are not available, then system 100, system 200 and method 300
default to a less desirable approach where the PPP/MLPPP protocol
state information is fully negotiated between the protection
chassis 145 and the working chassis 135 without the benefit of
direct communication there between by way of MC-APS control link
140.
[0053] It should be understood that, as used herein, the open state
refers to the circumstance where, as part of bringing PPP/ML-PPP
(for example LCP) up, when the layers successfully negotiate, the
layer specific parameters are "open" or "up." The down state
represents the converse.
[0054] FIG. 4 is a flow chart of an exemplary embodiment of a
method 400 for sending state information in resilient PPP/ML-PPP
services over multi-chassis APS protected routers. The method 400
starts in step 405 and proceeds to step 410.
[0055] In step 410, at least one packet is sent with a sequence
number. It should be apparent that, in various exemplary
embodiments, messages are bundled together. In such embodiments,
less CPU is used. Accordingly, bundling messages together achieves
an optimization of CPU resources. Accordingly, references herein to
the various steps in method 400 in either the singular or the
plural should be understood as references to both the plural and
the singular in the alternative. This should be also understood to
be a reference to various exemplary embodiments where packets are
sent singularly or bundled.
[0056] Following step 410, the method 400 proceeds to step 415. In
step 415 the packets sent in step 410 are received with their
sequence numbers.
[0057] Following step 415, the method 400 proceeds to step 420. In
step 420, an acknowledgement is sent that the packets were
received, again with the corresponding sequence numbers. In various
exemplary embodiments, an interval is set in which to receive
acknowledgements sent in step 420. Accordingly, in various
exemplary embodiments, steps 410, 415, 420 run repeatedly in
sequence and/or in parallel until a preset interval has
expired.
[0058] Following step 420, including the expiration of the
predetermined interval in some embodiments, the method 400 proceeds
to step 425. In step 425, an analysis is performed whether the
acknowledgements, including the sequence numbers, have been
received. If an acknowledgment with the corresponding sequence
number is never received, then the method 400 returns to step 410,
and the initial transmission is repeated.
[0059] Conversely, when an acknowledgement is successfully received
with the corresponding sequence number(s), the method 400 proceeds
from step 425 to step 430. In step 430, an analysis is made whether
there are any more packets that need to be transmitted. When a
determination is made in step 430 that at least one additional
packet needs to be sent, the method 400 returns to step 410 and the
steps of the method 400 are repeated. When a determination is made
in step 430 that no additional packets need to be sent, the method
400 proceeds to step 435 where the method 400 stops.
[0060] According to the foregoing, state information,
acknowledgements, message requests, and all other communications
described in connection with method 300 and method 400 occur
between the working chassis 135 and the protection chassis 145 by
way of MC-APS control link 140. Accordingly, various exemplary
embodiments achieve a quick restoration of services after an MC-APS
switchover. Likewise, various exemplary embodiments reduce data
outages during an MC-APS switchover.
[0061] The MC-APS 150 provides increased redundancy over single
chassis APS (SC-APS). This, in turn, affords the deployment of
time-sensitive applications over MC-APS protected ports and
circuits. Various exemplary embodiments achieve the foregoing
benefits without ever renegotiating the whole (ML)PPP
protocols.
[0062] Various implementations of the subject matter described
herein have achieved recovery time at or below a maximum of one and
a half seconds per port where the port(s) have around 500 entities.
Typically, the various exemplary embodiments described herein
recover from an APS switchover in about one second per port.
Accordingly, various exemplary embodiments recover from a router
failure with eight APS ports involving around 4000 PPP/MLPPP
entities, for example, in as little as eight to twelve seconds.
[0063] Although the various exemplary embodiments have been
described in detail with particular reference to certain exemplary
aspects thereof, it should be understood that the invention is
capable of other different embodiments, and its details are capable
of modifications in various obvious respects. As is readily
apparent to those skilled in the art, variations and modifications
can be affected while remaining within the spirit and scope of the
invention. Accordingly, the foregoing disclosure, description, and
figures are for illustrative purposes only, and do not in any way
limit the invention, which is defined only by the claims.
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